This invention relates to an instrument for making perspective drawing and more particularly to the lever and link arrangements adapted to have each set of parallel lines of objects come together automatically on the picture at their own vanishing point no matter how far apart that point may locate from or even though the point is clear off the drawing board.
It has heretofore been known in perspective drawing that frequently one or more vanishing points are found to be completely off the drawing board. In FIG. 1b, although a left vanishing point V1 is located on the drawing board DB, the other vanishing point V2 is outside of the drawing board. Further, in FIG. 1c, three vanishing points are all clear off the drawing board DB so that none of them may be indicated in th Figure. In FIG. 1a, although a single vanishing point V is within the same drawing board DB, that situation is usually lesser presented.
In such situations as shown in FIGS. 1b and 1c, a pin and a very long ruler or bar and the like are required in order to produce various lines exactly coming together at their own vanishing point outside of the drawing board. The pin is located at the outside vanishing point and the long ruler or bar is used in order to move the pencil therealong exactly toward the pin, for obtaining a correct perspective of box B.
While various means have been provided for making perspective drawing without using the long ruler and the pin, none has proven to be entirely sufficient.